1. Field of the Invention
This invention relates to new dispersions containing monovalent copper or silver ions or cations of polyvalent metals of polymers containing sulphonate groups, to a process for the production thereof by treating dispersions of polymers containing sulphonate groups with ion exchangers containing such cations, and to the use of these dispersions as coating agents for flexible or rigid substrates.
2. Description of the Prior Art
A large number of aqueous dispersions of polymers containing sulphonate groups or processes for the production thereof are already known. Thus, for example, aqueous dispersions of polyurethanes containing sulphonate groups or processes for the production thereof are described in the following publications: U.S. Pat. Nos. 3,479,310; 3,756,992; 4,108,814 and 4,092,286, British Pat. Nos. 1,076,688; 1,336,050 and 1,280,750, German Offenlegungsschriften Nos. 2,030,571; 1,954,090; 2,651,505; 2,725,589; 2,732,131; 2,634,576 and 2,811,148. Other polymer dispersions which contain sulphonate groups have been described, for example, by H. Warson in Polym. Paint Colour J. 164 (1974), No. 3879, P. 758-760; by M. S. Juang, IMM. Krieger in J. Polym. Sci., Polym. Chem. Ed. 14 (1976), No. 9, P. 2089-2107 or in German Offenlegungsschriften No. 2,549,650 and No. 2,526,717.
The fact is common to these pre-known dispersions of polymers containing sulphonate groups that the counterions to the incorporated sulphonate anions constitute alkali metal cations or monovalent ammonium cations, in particular those which are derived from tertiary amines. Thus, the polyurethanes are so-called "polyurethane ionomers", which, on one hand, are self-dispersible in water due to their salt character but, on the other hand, after the processing of the dispersions as coating agents, result in coatings whose water-resistance is still worth improving.
It has now surprisingly been found that it is possible to exchange the cations mentioned and present in the known polymer dispersions, in particular polyurethane dispersions, for cations of the undermentioned type, by treating the dispersions with conventional cation exchangers. This finding is surprising because it would be expected that treatment of the dispersions with cation exchangers would result in coagulation. Moreover, the finding was completely surprising that the polymer dispersions thus obtained, on one hand, are practically just as stable in storage as the starting dispersions and, on the other hand, they allow the production of coatings which have a clearly increased water-resistance. Within the scope of analytical experiments, dispersions which contain free sulphonic acid groups have indeed been converted into the silver salt. However, these were extremely dilute dispersions having a solid substance content of only 1 to 2%, in which silver ions were then analytically determined (O. Lorenz et al., Kautschuk, Gummi, Kunststoffe 33 (1980), P 527). Such extremely dilute dispersions obviously cannot be used for the conventional areas of use of aqueous plastics dispersions. Moreover, coagulation would naturally not be feared with such extreme dilutions.
Accordingly, it is an object of the present invention to produce dispersions as hereinafter set forth which are stable in storage and result in the production of coatings which have improved water resistance.